B entitlement: Vehicles up to 3,500kg Maximum Authorised Mass (MAM) carrying no more than 8 passengers plus driver with trailer up to 750kg; trailer over 750kg if combined vehicle and trailer weight isn’t more than 3,500kg MAM

Right so what's happening here is that we are mixing up a drivers ability to tow a vehicle & trailer i.e. their licence with what the actual towing vehicle can legally tow behind it regarding weight

Ignoring driving licence requirements from what I can find you can legally tow up to 100% of the vehicle manufacturers towing capacity figure. The 80-85% rule seems to be an advisory figure used by the likes of the caravan club etc and is more about the towing experience than the towing vehicles ability to do the job. Its a rule that's been about for a long time and it may well be outdated given how engine technology has moved on over the years.

When I was deliberating on a temporary tow car I searched the towing forums and cars with a relatively low kerb weight appeared to be good tow cars if they had the correct engine.

Having only towed the Sabre and trailer with Josh's GTE and my old Rangie I am certainly not experienced enough to make a judgement but I am now happy that I have the correct driving licence and that my new tow car when it finally arrives can legally do the job

Although the E category was slated when introduced, I firmly believe it's one of the best things they've ever done. Far too many accidents and deaths caused over the years by people who have hitched a badly loaded caravan up to the overloaded family car with no nose weight and wondered why they're suddenly upside down on the A303 at 70mph on a Friday afternoon!!

The 85% 'rule' is to do with stability & the towing vehicle's ability to control the trailer. At 85% & with a decent noseweight it's pretty much possible to guarantee stability: above 85% & it is more down to the type of tow car & the drivers ability and experience. Excluding other considerations most stable are cars with the rear wheels close to the tow ball. Absolutely essential is noseweight at or above 7% of the laden trailer weight: if you can just about lift the hitch onto the ball the noseweight is probably OK.